Abstract Bi–Sb–Te-based thermoelectric (TE) materials have attracted considerable attention for solid-state cooling and low-temperature waste heat recovery owing to their excellent thermoelectric performance. In this work, the influence of samarium (Sm) incorporation on the structural, electronic, and thermoelectric properties of Bi 1.5 Sb 0.5 Te 3 composites synthesized via solid-state reaction followed by sintering is systematically investigated. XPS confirms the formation of Sm-rich phases at localized regions, indicating composite formation. Room-temperature Hall measurements reveal a significant enhancement in carrier mobility from 2.7 to 23 cm 2 V −1 s −1 with Sm incorporation, leading to a reduction in electrical resistivity attributed to grain-boundary passivation and defect engineering. The pristine sample exhibits the highest Seebeck coefficient due to a lower density of states and Fermi level positioning closer to the valence band, resulting in a maximum power factor of 0.26 mWm −1 K −2 at 350 K. Although Sm incorporation reduces the power factor, it substantially enhances the thermoelectric figure of merit (ZT) through a pronounced suppression of lattice thermal conductivity arising from enhanced phonon scattering at grain boundaries and secondary phase interfaces. A maximum ZT of 0.035 at 350 K is observed for the 3% Sm-doped sample, representing a 13% improvement over the pristine material. The present study provides mechanistic insights into the composite engineering of n-type Bi 1.5 Sb 0.5 Te 3 , demonstrating the effect of rare-earth inclusion as a composite dopant in the Bi–Sb–Te alloy and its impact on thermoelectric properties.
Poojitha et al. (Wed,) studied this question.